The present invention relates to an air cleaner element and a method of manufacturing the same, and more particularly to an air cleaner element for use in an air cleaner for an internal combustion engine, and a method of manufacturing such an air cleaner element.
It is generally known that air cleaner elements for use in air cleaners for internal combustion engines are available in dry and wet types. In both dry and wet types, the air cleaner elements mainly rely on surface filtration and depth-type filtration. It is important that such air cleaner elements have a filtration ability to effectively separate minute particles such as dust particles from a fluid to be filtered and keep a good filtration ability for a long period of time.
Various air filter elements have been proposed to meet the above requirements. Air filter elements of the surface filtration type include an air filter element having filter paper with its surface napped, an air cleaner element with its surface roughened by a special process to increase the actual surface area, and an air cleaner element coated with a special sticky material or oil for facilitating the formation of a dust cake layer and also for a longer service life. Air filter elements based on the depth-type filtration include an air filter element composed of filter paper layers of different fiber densities to provide a density gradient in the transverse direction of the filter paper.
Air cleaners for internal combustion engines employ air filter elements described above. One conventional air cleaner for use with an internal combustion engine is illustrated in FIGS. 23 and 24 of the accompanying drawings. The air cleaner, generally indicated by the reference numeral 21, comprises a cylindrical cleaner element 23 disposed in an air cleaner case 22 and constructed of a filter paper layer bent into a number of folds. Air to be filtered is drawn from an inlet 22i into the air cleaner case 22 and flows along the inner peripheral surface of the air cleaner case 22 and across the cylindrical element 23 from its outer peripheral side to its inner peripheral side. At this time, the air is filtered by the cleaner element 23, and only cleaned air from which dust is separated is discharged from an outlet 22o.
The conventional air cleaner element is disadvantageous in that since there is an area limitation between the air cleaner case and the cleaner element, the length of the air flow path is irregular (e.g., the air flow path up to a point b is longer than the air flow path up to a point a), and the speed of the air flow is not uniform on various portions of the cleaner element. For this reason, the resistance of the filter paper of the cleaner element to the air flow is not uniform, and the air flows through the filter paper at different speeds at various areas of the filter paper, so that uniform filtration cannot be achieved.
The process of manufacturing the conventional air cleaner element has limitations such that very thin cleaner elements having a thickness of from 10 to 15 mm, for example, cannot be produced easily. Even if such a thin cleaner element could be manufactured, the cross-sectional area of the air flow path would be greatly reduced, and the resistance to the air flow would be increased. When an air cleaner element is designed to maintain a desired cross-sectional area of air flow path with a view to lowering the resistance to the air flow, the air cleaner element becomes relatively thick, and hence a substantially thin air cleaner element cannot be obtained.